The present application claims priority to Japanese Application(s) No(s). P2000-326120 filed Oct. 25, 2000, which application(s) is/are incorporated herein by reference to the extent permitted by law.
1. Field of the Invention
The present invention relates to a magnetoresistance-effect magnetic head that utilizes magnetoresistance effect to read signals magnetically recorded on a magnetic recording medium.
2. Description of the Related Art
Recording/reproducing apparatuses using a magnetic tape as a recording medium, such as a video tape recorder and a digital data recorder, are known. In such a recording/reproducing apparatus, the magnetic head writes and reads magnetic signals on and from the magnetic tape running in the apparatus, while kept in contact with the magnetic tape.
Recording/reproducing apparatuses of this type, which use a magnetic type have been modified, reducing the wavelength of signals to record data at high-density. To accomplish high-density recording, it is attempted to incorporate a magnetoresistance-effect magnetic head (hereinafter referred to as xe2x80x9cMR headxe2x80x9d) into recording/reproducing apparatuses that use a magnetic tape. This is because the magnetoresistance-effect magnetic head can reproduce signals with high efficiency.
The MR head has hitherto been used as a data-reproducing head, mainly in hard disc drives. The MR head for use as a data-reproducing head in a hard disc drive has a magnetoresistance-effect element (hereinafter referred to as xe2x80x9cMR elementxe2x80x9d) that has magnetoresistance effect. The MR element is exposed at that surface of the MR head, which opposes the magnetic disc used as a recording medium in the disc drive. Thus exposed, the MR element can detect the signal magnetic field emanating from the magnetic disc.
The MR head is used as a data-reproducing head in recording/reproducing apparatuses using magnetic tape, too. In such a recording/reproducing apparatus, the MR head contacts the tape running while the MR head recording data on, or reproducing data from, the tape. The MR element of the MR head is exposed to the recording medium, i.e., the tape. As the tape runs, sliding on the MR element, the MR element gradually wears, changing the characteristics of the MR head gradually. Additionally, the operating reliability of the MR head decreases due to the noise made as the tape runs in sliding contact with the MR element. In view of this it is desired that an MR head for use in recording/reproducing apparatuses using magnetic tape should have an MR element that is not exposed to the magnetic tape, i.e., the recording medium.
A so-called xe2x80x9cflux-guiding MR headxe2x80x9d has been proposed as an MR head having an MR element not exposed to the recording medium. The flux-guiding MR head has a flux-guiding element that is made of, for example, soft magnetic thin film. The flux-guiding element is arranged, with its one end exposed to the recording medium. The flux-guiding element can therefore guide the signal magnetic field emanating from the recording medium, to the MR element.
FIG. 1 shows an example of a flux-guiding MR head 100. As shown in FIG. 1, the flux-guiding MR head 100 comprises a pair of magnetic shield layers 101 and 102, an MR element 104, and a flux-guiding element 105. The magnetic shield layers 101 and 102 are spaced apart. The layer 102 is positioned above the layer 101, providing a gap 103 between the layers 101 and 102. The MR element 104 and the flux-guiding element 105 are arranged in the gap 103. The flux-guiding element 105 has one end positioned near the surface 100a of the MR head 100, which faces the recording medium. Thus, this end of the flux-guiding element 105 is exposed at the surface 100a and opposes the recording medium. The MR element 104 is positioned at a longer distance from the surface 100a than the flux-guiding element 105 and is not exposed at the surface 100a. 
In the flux-guiding MR head 100, the flux-guiding element 105 guides the signal magnetic field emanating from the magnetic recording medium, to the MR element 104. The resistance of the MR element 104 varies in accordance with the signal magnetic field guided to the MR element 104. The change in the resistance of the MR element 104 is detected as a voltage change, whereby a magnetic signal is read from the magnetic recording medium. As described above, the MR element 104 is not exposed at the surface 100a that faces the recording medium and does not contact the recording medium. The MR element 104 never wear or make noise while the recording medium, i.e., tape, is running. Hence, the MR head 100 can read the magnetic signal from the recording medium, without degrading the operating reliability.
In the flux-guiding MR head 100 of the structure described above, it is desired that the distance between the MR element 104 and the flux-guiding element 105 be as short as possible. The shorter the distance, the more efficiently the signal magnetic field can be transmitted from the flux-guiding element 105 to the MR element 104. The hither the field-transmitting efficiency, the greater the magnitude of the output. If the MR element 104 and the flux-guiding element 105 contact, however, a part of the sense current to be supplied to the MR element 104 will flow to the flux-guiding element 105. To prevent the sense current from flowing to the flux-guiding element 105, it is necessary to space the MR element 104 and the flux-guiding element 105 apart from each other by a very short distance in the flux-guiding MR head 100 that has the structure specified above.
A gap is provided between the MR element 104 and the flux-guiding element 105 in a specific manner. As FIG. 2 shows, an electrically insulating film 106 is formed, covering the MR element 104, before the flux-guiding element 105 is formed. Once the flux-guiding element 105 is formed, that part of the film 106, which is deposited on one side of the MR element 104 lies between the MR element 104 and the flux-guiding element 105, spacing the MR element 104 from the flux-guiding element 105. The gap between the elements 104 and 105 is therefore determined by the thickness of that part of the electrically insulating film 106.
Here arises a problem. It is extremely difficult to control the thickness of the insulating film 106 deposited on said side of the MR element 104, with high precision of nanometer order. In the flux-guiding MR head 100 of the structure described above, the operating efficiency of the MR element 104 will sharply decrease even if the distance between the MR element 104 and the flux-guiding element 105 changes a little. In view of this it is considered very difficult to manufacture, in a high yield, flux-guiding MR heads that can generates outputs of large magnitude.
The present invention has been made in view of the foregoing. An object of the invention is to provide a flux-guiding MR head in which the distance between the magnetoresistance-effect element and the flux-guiding element can be controlled with high precision and which can therefore generate a large output.
A magnetoresistance-effect element and a flux-guiding element can be spaced apart from each other by forming an electrically insulating film between them. It is relatively easy to control the thickness of the insulating film, as measured in the direction of depositing the insulating film. Hence, the distance between the magnetoresistance-effect element and the flux-guiding element can be controlled with high precision, only if the elements are formed at different levels, one overlapping the other.
In a magnetoresistance-effect magnetic head of the structure described above, the efficiency of transmitting a signal magnetic field from the flux-guiding element to the magnetoresistance-effect element greatly depends not only on the distance between these elements, but also on the distance for which the elements overlaps each other. It follows that the signal magnetic filed can be very efficiently transmitted from the flux-guiding element to the magnetoresistance-effective element if the distance between these elements and the overlapping distance thereof are set at optimal values. The flux-guiding MR head can then generates a large-magnitude output.
A magnetoresistance-effect magnetic head according to the invention has been devised based on the finding described above. The flux-guiding MR head has a medium-facing surface and comprises an upper magnetic shield layer, a lower magnetic shield layer, an inter-shield gap, a magnetoresistance-effect element, and a flux-guiding element. The inter-shield gap is provided between the upper and lower magnetic shield layers. The magnetoresistance-effect element is provided in the inter-shield gap and is not exposed at the medium-facing surface. The flux-guiding element has one end exposed at the medium-facing surface. It guides an external magnetic field to the magnetoresistance-effect element. In the flux-guiding MR head, the magnetoresistance-effect element is arranged at a different level from the flux-guiding element. An electrically insulating film is interposed between the magnetoresistance-effect element and the flux-guiding element. That part of the magnetoresistance-effect element which lies close to the medium-facing surface overlaps that part of the flux-guiding element which lies remote from the medium-facing surface. The magnetoresistance-effect element overlaps the flux-guiding element for a distance that falls within a range of 15 to 25% of the length of the magnetoresistance-effect element as measured in a direction perpendicular to the medium-facing surface.
The magnetoresistance-effect magnetic head can read magnetic signals from a magnetic recording medium, while set in contact with the magnetic recording medium. That is, the flux-guiding element, which has one end exposed at the medium-facing surface, guides the signal magnetic field emanating from the medium, to the magnetoresistance-effect element, which reads the signals recorded on the medium, by utilizing its magnetoresistance effect.
The shorter the distance between the magnetoresistance-effect element and the flux-guiding element, the more efficiently the signal magnetic field can be transmitted from the flux-guiding element to the magnetoresistance-effect element. The distance can be maintained short to a precise value in the magnetoresistance-effect magnetic head according to the invention, for the following reason. The magnetoresistance-effect element is arranged at a different level from the flux-guiding element. Therefore, that part of the magnetoresistance-effect element which lies close to the medium-facing surface overlaps that part of the flux-guiding element which lies remote from the medium-facing surface, with the electrically insulating film interposed between the magnetoresistance-effect element and the flux-guiding element. Thus, the distance between the elements can be accurately adjusted, merely by controlling the thickness of the electrically insulating film. The efficiency of transmitting the signal magnetic field from the flux-guiding element to the magnetoresistance-effect element is thereby enhanced. Hence, the magnetic head can reproduce signals from the medium with high efficiency.
The efficiency of transmitting the signal magnetic field from the flux-guiding element to the magnetoresistance-effect element depends upon the distance by which the magnetoresistance-effect element overlaps the flux-guiding element. In the magnetic head of this invention, the magnetoresistance-effect element overlaps the flux-guiding element for a distance that falls within a range of 15 to 25% of the length of the magnetoresistance-effect element as measured in a direction perpendicular to the medium-facing surface. This increases the efficiency of transmitting the signal magnetic field from the flux-guiding element to the magnetoresistance-effect element even more. The magnetic head can therefore reproduce signals from the medium with an even higher efficiency.
In the magnetoresistance-effect magnetic head according to this invention, the magnetoresistance-effect element is arranged at a different level from the flux-guiding element. The part of the magnetoresistance-effect element which lies close to the medium-facing surface, therefore, overlaps that part of the flux-guiding element which lies remote from the medium-facing surface, with the electrically insulating film interposed between the magnetoresistance-effect element and the flux-guiding element. Hence, the distance between the elements can be accurately adjusted, merely by controlling the thickness of the electrically insulating film. The efficiency of transmitting the signal magnetic field from the flux-guiding element to the magnetoresistance-effect element is thereby enhanced. The magnetic head can reproduce signals from the medium with high efficiency.
In the magnetoresistance-effect magnetic head of the invention, the magnetoresistance-effect element overlaps the flux-guiding element for a distance that falls within a range of 15 to 25% of the length of the magnetoresistance-effect element as measured in a direction perpendicular to the medium-facing surface. This makes it possible to transmit the signal magnetic field from the flux-guiding element to the magnetoresistance-effect element, even more efficiently. The magnetic head can therefore reproduce signals from the medium with an even higher efficiency.